And that matters when the speaker has a constant vertical directivity down to Schroeder? Please explain why.
Ever heard about a bandlimited ETC BTW?
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Constant Beamwidth Transducer (CBT) Speakers
- Thread starter Rick Sykora
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Ever heard about a bandlimited ETC BTW?
markus
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That's exactly the question – does it really have "constant vertical directivity down to Schroeder?" Please post data showing this. I can't remember seen it published. Is it somewhere in Keele's papers?
Yep, and it's of limited value for showing the claimed behavior with the Schroeder frequency – and a large transition zone around it – usually at around >200Hz in acoustically small rooms.
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Yes, pretty much.
This is from Keele’s modelling:
Keele, A Performance Ranking of Seven Different Types of Loudspeaker Line Arrays, 2010
He also did actual measurements and essentially confirmed the model for vertical. I need to dig further to find them.
cheers
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markus
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Thanks, remember those theoretical calculations when I read the Keele papers back then. Would like to see Bjorn's claim of "20dB attenuation" confirmed for a real design though.
And again, an ETC won't do even when band-limited. You'll fight frequency vs time resolution and in the end graphs aren't as conclusive as desired. One would need to look at free field data instead.
A 20dB attenuation at a 40-60 degrees angle is pretty hard to do. Something like a Quad ESL-57 does it.
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Look at some of the papers that Richard Taylor wrote with Don Keele -
dziemian
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Does it work well with Dirac Live? Dirac Lives measures and corrects single speakers. How is it suppose to work with multiple speakers playing at diffrent time and distance?
Have not tried it with Dirac Live. The arc is necessary for proper phasing of the drivers. The speaker looks like a virtual point source radiator at the center of the arc. It is the straight linear array that doesn't phase correctly unless it goes from the floor to the ceiling and both the floor and the ceiling are reflective. Then the reflections make the line radiator look like an infinite line source. The shading is something that has been used in radar antennas since WW II (it's called a shaded aperture) to get rid of side lobes. To make the CBT work you need both the arc and the shading. Large planar radiators (electrostatic or magnetic) patterns go to shit once the radiated wavelength becomes larger than a speaker dimension. This is all about diffraction from extended sources. I think an awful lot of high end speaker manufactures ignore these effects. My other speakers are Linkwitz LX521.4.
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I don’t have a big enough living room to accommodate them for surround
My couch is against the back wall, so I used JBL CBT50 mounted to the sides.
A floor standing CBT has several advantages of a free standing. Or, one could alter the shading network and mount the rear/surround CBT in the ceiling. If the ceiling height fits the CBT speaker height, that's likely the best option for a surround speaker.
However, whether a surround speaker should have wide dispersion is up for debate. Generally though, a wide and constant directivity is better than narrow one where the directivity collapses (become wider) quite high in frequency. The latter is what we see with most speakers and IMO that's simply not a great design not matter what Spinorama score they achieve.
However, whether a surround speaker should have wide dispersion is up for debate. Generally though, a wide and constant directivity is better than narrow one where the directivity collapses (become wider) quite high in frequency. The latter is what we see with most speakers and IMO that's simply not a great design not matter what Spinorama score they achieve.
Here is my home theaters (surround sound has never sounded right to me when I tried it so I just use stereo) -
You might find the papers Richard Taylor wrote in collaboration with Don Keele of interest -
I also found this link. Maybe someone other than JBL is going to be making commercial CBT's again -
You might find the papers Richard Taylor wrote in collaboration with Don Keele of interest -
I also found this link. Maybe someone other than JBL is going to be making commercial CBT's again -
OP
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Slow cabinet manufacturer but it's on the way.maybe someday. right @Bjorn?
Things have been moving slowly with a new and improved groundplane CBT speaker for several reasons. But stuff is happening now, and I'll share more details in dealers forum when we're ready.
Keith_W
Major Contributor
Do you think you could get improved performance if you were to use a series of dual concentric drivers like that used in the KEF LS50/LS60?
you need a minimum grid distance between the drivers to make it work well, I guess the KEF drivers are to large for that
pt6825 would be good for >200Hz
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